&#34;B stageable&#34; high service temperature epoxy thermosets

ABSTRACT

A B stageable thermosettable composition containing at least one polyepoxide and at least one linear anhydride monomer capable of forming a cyclopolymer in situ and processes for the formation of the B stage intermediate and final thermoset having a high service temperature is provided. The composition is useful in a two stage process; first to form a storage stable, flowable thermoplastic B stage intermediate by the free radical initiated vinyl polymerization of the linear anhydride in the liquid composition to a cyclic polymer and secondly to react the cyclic polymer with the poly epoxide to form a crosslinked high service temperature thermoset useful in the preparation of laminates, such as printed circuit boards, adhesives, and encapsulants.

FIELD OF THE INVENTION

This invention is directed to the use of a linear anhydride monomer,capable of forming a cyclopolymer, as a curing agent in a "B stageable"polyepoxide-containing thermosettable, preferrable liquid, compositionuseful for forming high service temperature thermosets. Moreparticularly the invention is directed to a liquid composition, which ispreferably solvent-free, containing a (meth)acrylic anhydride curingagent and at least one polyepoxide wherein the anhydride is firstcyclopolymerized in situ without significantly crosslinking with thepolyepoxide so to form a semi-solid or gel, flexible and flowablethermoplastic (B stage) that is stable upon storage at room temperature,and which can be subsequently cured at elevated temperatures, throughthe crosslinking reaction of the cycloanhydride polymer and polyepoxide,to form a high service temperature thermoset.

BACKGROUND OF THE INVENTION

Manufacturers of electronic circuitry and components desirethermosettable compositions to prepare laminates, such as printedcircuit boards, adhesives, such as die-attach adhesives, andencapsulants having high service temperatures. "High servicetemperature" polyepoxide thermosets as used herein refers to threedimensionally crosslinked materials having a glass transitiontemperatures (Tg) on the order of at least 130° C., and preferably 180°C. or higher.

Liquid thermosettable compositions which can be partially polymerized orcured to form an intermediate solid, semi-solid, or gel thermoplasticthat is stable and storable at room temperature in the semi-solid form,and easily handled and capable of being formed into desired end productconfigurations prior to the formation of a final cured thermoset aredesired. These intermediate semi-solid materials are referred to hereinas "B stage" materials; the liquid compositions that can be formed intosuch storage stable, but flowable thermoplastic intermediates arereferred to as "B stageable" and processes for forming the intermediateare referred to as "B staging".

"Polyepoxides" as used herein refer to a polymer or polymer mixturewherein at least one polymer contains at least two epoxide, ##STR1##Fuctional Groups. Conventional polyepoxide thermosettable compositionscontaining curing agents, optionally with accelerators, for the curingor crosslinking reaction of the polyepoxide with the curing agent areknown and are capable of forming high service temperature thermosets.When curing agents that are non-reactive with polyepoxides at roomtemperature are employed in combination with accelerators, that do notinitiate or catalyze the curing reaction at room temperature, thecompositions can be stored in the liquid state for some time prior tocuring. However, because of the rapid exothermic reaction ofconventional curing agents with polyepoxides upon heating to elevatedtemperatures, it is often extremely difficult or impossible upon theapplication of heat to prevent the composition from rapidly proceedingfrom the liquid form directly to the final three-dimensionallycrosslinked thermoset without forming a desirable B stage thermoplastic.Further, since the final service temperature of the thermoset is adirect function of the temperature employed for the curing reaction, itis often difficult or impossible to obtain a very high servicetemperature thermoset (Tg greater than 150° C.) because of the rapidonset of curing once the minimum elevated temperatures needed toinitiate curing is reached. Complicating this situation is the fact thatmost liquid polyepoxide thermoset compositions are formulated in organicsolvents. While the majority of the organic solvent used to formulateconventional polyepoxide thermosets volatilizes upon the application ofelevated temperatures, some solvent can remain trapped in the thermosetresulting in a less than a 100% solid thermoset product havingundesirable physical properties for certain applications. In addition,the presence of organic solvents in the liquid polyepoxide compositionmay present solvent removal, flammability and potential health problems.

DESCRIPTION OF THE PRIOR ART

Many acid anhydrides, having at least two acid groups per molecule, areknown to be useful as curing agents for polyepoxides. Chapter 12 of TheHandbook of Epoxy Resins, Lee and Neville, McGraw-Hill (1982) presentsan excellent review of acid anhydride curing agents. The acid anhydrideswhich have been used as curing agents for polyepoxides include alicyclicanhydrides, aromatic anhydrides, chlorinated and brominated anhydrides,and some types of polymeric linear aliphatic anhydrides. Monomericaliphatic anhydrides, however, have as a class been viewed as beingunsuitable as polyepoxide curing agents since these anhydrides typicallysplit to yield monofunctional carboxylic acid molecules. While eachmonocarboxylic acid molecule can react with a polyepoxide,monofunctional acids cannot react with polyepoxides to form the threedimensionally crosslinked network needed for a useful high servicetemperature thermoset. Certain linear polymeric anhydrides, such asthose derived from the inter-molecular condensation of organic acids,can be used as polyepoxide curing agents since they arecarboxyl-terminated polymers containing internal anhydrides, having thegeneralized structure HO [OC(CH₂)_(x) C00 ]H where n is at least 2, thatprovide the necessary difunctionality needed for the polyepoxidecrosslinking reaction. Typical of these linear polymeric anhydridesuseful with polyepoxides are polysebacic acid anhydride and polyazelaicacid anhydride. Linear polyanhydrides of the above type have also beenemployed as blends with certain monomeric anhydrides such ascycloaliphatic anhydrides, for example; hexahydrophthalic anhydride(HHPA), dodecylsuccinic anhydride (DDSA), an Nadic Methyl Anhydride®(NMA), a trademark of Allied Chemical Corporation, and aromaticanhydrides such as phthalic anhydride.

Linear monomeric anhydrides which are capable of polymerizing in situ inpolyepoxide liquid thermosettable compositions, such as (meth)acrylicacid anhydride, have not, however, been reported as being useful bythemselves as curing agents for polyepoxides.

U.S. Pat. No. 3,676,398 is directed to polymerizable diester-derivativemonomers which can undergo subsequent vinyl polymerization with itselfor another vinyl monomer or polymer to form crosslinked infusiblematerials. This patent discloses the formation of the polymerizablediester-derivative monomer by the reaction of a polyepoxide with anacryloyl carboxylic acid anhydride. The acryloyl carboxylic acidanhydride is illustrated as being the reaction product of two differentcarboxylic acids; one of which can be methacrylic acid. These anhydridereaction products, however, are not disclosed or suggested as including(meth)acrylic acid anhydride monomer or a material containing a(meth)acrylic acid anhydride monomer.

Itaconic and maleic anhydride are also well known curing agents forpolyepoxides (See U.S. Pat. No. 4,503,200), however, since they exist ascyclic structures in monomeric form they are not disclosed or suggestedin the art as being capable of forming useful B stage intermediates.Applicant shall demonstrate hereinafter by actual comparative examplesthat such cyclic anhydride monomers are not suitable in the practice ofthe present invention.

Numerous references exist disclosing the use of alicylicanhydride-containing polymers of styrene and maleic anhydride as curingagents for polyepoxides. Examples of such references include U.S. Pat.Nos. 2,781,333, 2,858,323 and 2,848,433, 3,732,332 and Japan Kokai No.81-92911. These polymeric anhydrides are incapable, however, of forminga stable B stage intermediate because of their reactivity withpolyepoxides.

Russian Pat. No. 574,452 is related to the production of copolymers of(meth)acrylic esters and vinyl monomers. These copolymers are disclosedas being prepared by the free radical copolymerization of a vinylmonomer, specifically methyl methacrylate, with methacrylic acidanhydride and an epoxy compound, where the methacrylic acid anhydrideand epoxy are present in an equimolar ratio. The patent teaches theformation of di/poly functional polymeric methacrylate. It is not,however, directed to a liquid B stageable thermoplastic or to a highservice temperature polyepoxide thermoset. In addition, applicant'sliquid polyepoxide composition does not require the need for methylmethacrylate or any other such monofunctional monomer in combinationwith the polyepoxide and (meth) acrylic anhydride curing agent to formthe B stage or final thermoset.

It is an object of the invention to use a linear anhydride monomer whichhas the capability of homopolymerizing in situ in a composition,containing a polyepoxide without initially or significantly crosslinkingwith the polyepoxide, to form a B stage thermoplastic which is flexible,flowable, and stable upon storage, and which can be cured to form a highservice temperature thermoset.

It is a further object of the invention to provide a solvent-free, Bstageable thermosettable composition capable of yielding a high servicetemperature (100% solid) thermoset without the disadvantages of organicsolvents.

It is an additional object of the present invention to provide athermosettable B stageable composition which can be used in thefabrication of printed circuit boards, die-attach adhesives andencapsulants for electronic circuitry having a glass transitiontemperature higher than 150° C., preferably higher than 180° C. and mostpreferably higher than 225° C. These objects of the invention and otherswill become apparent from the following detailed description andillustrative examples which follow.

SUMMARY OF THE INVENTION

This invention is directed to a composition containing a polyepoxide anda linear anhydride monomer capable of forming a stable B stagethermoplastic intermediate and a high service temperature thermoset. Itis also directed to processes for forming the B stage intermediate andhigh service temperature solid thermoset from the composition andprocesses for using the compositions for preparing laminates, adhesivesencapsulants.

DETAILED DESCRIPTION OF THE INVENTION

The thermosettable composition of the present invention contains apolyepoxide and a linear anhydride monomer. The polyepoxide may be anyepoxide polymer or mixture containing at least one epoxide polymercontaining at least two epoxide, ##STR2## functional groups. Thepolyepoxide may be any such material known in the art and can besaturated or unsaturated, aliphatic, cycloaliphatic, heterocyclic, oraromatic. It may be also be substituted with various groups such as forexample, halogens. One preferred class of polyepoxides useful in thepractice of the invention are epoxidized esters having a least two epoxygroups such as for example; 2,3-epoxybutyl 3,4-epoxypentanoate,epoxycyclohexanol epoxycyclohexanoate (e.g. Union Carbide Corporation'sERL® 4221) and the like. Another preferred class are bisphenolderivatives such as for example; epicholorohydrin- bisphenol adductsincluding Shell Epon® 828, and bis-4,4¹ -(2¹,3¹ -epoxypropyl)dibromophenyl propane, such as for example Dow Chemical's Quatrex® 6410,and the like. Other preferred polyepoxides include epoxycresol novolaksand epoxyphenol novolaks.

The linear anhydride monomers which can be used in the practice of theinvention are selected from the group of linear anhydride monomers thatcan form a linear cyclopolymer by a free radical vinylhomopolymerization reaction in the presence of a polyepoxide withoutsignificant crosslinking therewith. The linear cyclopolymers so formedsubsequently open during the curing or crosslinking reaction with thepolyepoxide while maintaining their linear polymeric chain structurewithout degradation of the polymer backbone. For example, methacrylicanhydride monomer (MACAN) has the structural formula: ##STR3## The MACANmonomer homopolymerizes by a free radical vinyl polymerization to form alinear cyclopolymer having the structural formula: ##STR4## This linearcyclopolymer can open during the curing reaction with polyepoxideswithout losing its linear polymeric chain structure and withoutdegradation of its molecular weight.

Polymeric (non) cyclicanhydrides formed from cyclic anhydride monomerssuch as polyazelaic anhydride polymer and copolymers are notcontemplated within the class of linear anhydride monomer curing agentsof the present invention, since such polymers do not have the capabilityof ring opening during cure while maintaining a rigid linear polymerchain without molecular weight degradation.

While MACAN is the preferred linear anhydride curing agent for use inthe composition of the invention, acrylic anhydride (ACAN), mixtures ofmethacrylic acid anhydride and acrylic anhydride, and the like may alsobe employed.

It is preferred that the polyepoxides and monomeric linear anhydridecuring agents used in the composition of the invention are liquids atroom temperature or that they are capable of forming solutions ordispersions with one another at room temperature.

The molar ratio of monomeric linear anhydride curing agent topolyepoxide in the composition can vary from as low as about 0.4/1.0 toabout 1.0/1.0. Preferably the molar ratio of monomeric linear anhydrideto polyepoxide is in the range of about 0.6/1.0 to 1.0/1.0, and mostpreferably from about 0.8/1.0 to 1.0/1.0.

The amount of polyepoxide and monomeric linear anhydride in thecomposition is a function of the amount of additives, initiators,accelerators, fillers, pigments, mold lubricants, reinforcement agentsand the like which can be added to the composition. It is preferred notto utilize any solvent in the composition for the reasons set forthhereinbefore.

In order to form a B stage intermediate it is necessary for freeradicals to be present, or become present in the composition to initiatethe vinyl homopolymerization of the linear monomeric anhydride to alinear cyclopolymer. Free radicals can be supplied from the compositionitself without the addition of free radical generators or by theaddition of free radical generating compounds to the composition. Onemechanism for generating free radicals for B staging the compositionwithout adding free radical generating compounds is by exposing thecomposition to short wavelength actinic radiation, such as for exampleelectron beam radiation. Another less preferred mechanism is to subjectthe composition to an elevated temperature, on the order of from about50° C. to about 80° C., but below the temperature required to initiatethe polyepoxide-anhydride curing reaction, for an extended time. Thismechanism is not preferred, however, because if the epoxide anhydridecrosslinking reaction temperature were to be accidentally reached, thecomposition could proceed directly from the liquid, past a B stage, anddirectly to a solid thermoset. Heating the liquid composition toelevated temperatures below the critical temperature is also not apreferred means for forming the B stage intermediate because of thelength of time needed to form a desirable B stage material. Anotherpreferred mechanism for B staging the liquid composition is by the useof ultra-violet (UV) radiation exposure coupled with the addition of aphotoinitiating free radical generating compound or mixture to theliquid composition. The photoinitiating compound or mixture should beselected such that the compound or mixture will generate a sufficientamount of free radicals for the vinyl cyclo-homopolymerization reactionof the monomeric linear anhydride preferably at room temperature.Suitable photoinitiating compounds for room temperature UV exposureinclude azobis-isobutyronitrile and related azobisnitriles such as thoseof the E. I. DuPont de Nemours Vazo® series. Other suitable UVphotoinitiators include benzoin, alkoxy acetophenones, hydroxy alkyl -or hydroxy cycloalkyl aryl ketones, and the like. No special precautionsor filtration of the light source is required for the UV exposure;conventional "black light" sources may be used. An additional preferredmechanism for B staging the composition involves the addition of freeradical generating compounds which yield free radicals at temperatureshigher than room temperature, but lower than the polyepoxide-anhydridecuring temperature. These free radical generators are conventionalmaterials well known to those of ordinary skill in the art including forexample, benzoyl peroxide, t-butyl peracetate, azobis(isobutyronitrile), azobis (dimethylvaleronitrile); azobis(dimethylmethoxybutyronitrile) and the like. When free radicalinitiators are added to the composition typically they are added at aconcentration of from about 0.1 to about 5.0 weight percent based on theweight of the anhydride monomer present in the composition. It is alsopossible, but not practical or preferred, to B stage the composition bythe addition of free radical initiator which produce free radicals atroom temperature, however, such initiators must be handled attemperatures below room temperature and accordingly are difficult tohandle and control.

The composition is B staged until a semi-solid or gel having desiredviscosity and other physical properties are achieved. After thecomposition is B staged to form a semi-solid or gel, it may be stored atroom temperature in the gel state for a period of about 2 weeks or atdepressed temperature, for example at about 40° F., for up to about 1month. The B stage material is flexible and practical; it can be moldedinto the desired shape, applied to substrate surfaces and the like inpreparation for final curing.

To cure the B stage material to a three dimensionally crosslinkedthermoset, the B stage is then heated to a temperature of at least about150° C., preferably to a temperature of 180° C. and in some cases totemperatures as high as about 250° C. for a sufficient time, usually onthe order of several hours, to form the thermoset.

The time for the final curing reaction can be accelerated by theaddition of conventional polyepoxide-anhydride accelerators to thestarting liquid composition. These accelerators include for exampletertiary amines such as; benzyldimethyl amine or 2,4,6,-tri(dimethylamino)phenol; quaternary amines such as benzyl trimethyl ammoniumchloride, phosphines such as triphenylphosphine, and other Lewis bases.A preferred accelerator for the composition has been found to bebenzyltrimethylammonium chloride. When accelerators are added to theliquid composition, they are included in amounts conventional in theart, for example, at concentrations of from about 0.1 to about 5.0percent by weight of the polyepoxide-anhydride composition.

The resultant thermoset is a 100% solid material having a servicetemperature as high as the final curing temperature.

As mentioned previously, various other ingredients may be mixed with thecomposition including fillers, pigments, dyes, mold lubricants,reinforcements and the like. It is preferred that no more than 80 weightpercent of the composition contain such other ingredients. It is alsopreferred not to utilize, as a diluent, any monofunctional monomer in anamount greater than 20 weight percent since such monomers may have anegative effect on the tractability of the B stage and could severleyreduce the service temperature of the final thermoset. Certainreinforcing agents such as glass, fiberglass, Kevlar® E. I. DuPont,which is an aromatic polyamide, silica, mica, talc, calcium carbonate,mixtures thereof and the like may be used in various amounts to achievedesired thermoset physical properties for specific end uses. Inpreparing laminates, such as printed circuit boards, from thecomposition, the preferred additives are glass mat, Kevlar mat, wovenglass cloth, non-woven glass strands or non-woven Kevlar strands, any ofwhich being wettable by the composition.

The following examples are provided to illustrate the present invention,and are not intended to limit the scope of the invention. All amountsare by weight unless otherwise indicated.

EXAMPLE 1

A mixture of methacrylic anhydride (MACAN) (111 parts), epoxycyclohexylepoxycyclohexanoate (Union Carbide Corporation ERL® 4221) (120 parts),benzyltrimethylammonium chloride accelerator (BETAC) (1.2 parts), and0.25 parts of (azobis(dimethylvaleronitrile)) initiator (E. I. duPont deNemours, Inc.'s Vazo® 52 brand) were mixed in the absence of water andin the presence of air. The mixture was then charged to a roomtemperature mold (1/8"×4"×4") and the mold was then placed in an 80° C.oven. In about 1 hour the mold was observed and gelation to a "B"-stageresin had occurred. The gel was then removed from the mold and thenfurther heated at 150° C. for four hours to accomplish final curing. Theglass transition temperature (Tg) was then determined using a E. I.duPont Thermal Analyzer by the penetration probe method. No Tg wasdetected up to a temperature of 225° C.

EXAMPLE 2 Laminate Manufacture

A mixture of MACAN (64.5 parts), bis (epoxypropyldibromophenyl)propaneDow Chemical Company's Quatrex® 6410 brand) (39 parts), ERL® 4221 (46.5parts), Vazo® 52 free-radical initiator (0.51 parts) andbenzyldimethylamine accelerator (BDMA) (1.5 parts) were mixed in air asin Example 1, and then degassed under vacuum. A glass fabric wasimpregnated with the mixture by dipping the mat at an acute angle to andinto the liquid mixture forcing entrapped air from the fabric. Thefabric was removed from the mixture and allowed to drain in air. Theimpregnated fabric was then heated at 50° C. until gelation had occurred(about 1 hour). The impregnated fabric was cut in several sections andstacked. The stacked fabric was then pressed in a hot press at 225° C.for four hours to produce a laminate. The resulting laminate had a Tg(as measured by the technique used in Example 1) of 225° C.

EXAMPLE 3(Comparative) Casting

In this example, mixtures were made with various unsaturated anhydridesand examined for their casting and subsequent flow behavior. In Examples3-E and 3-F, the amount of epoxy resin was reduced to maintain theepoxy/anhydride stoichiometry. Sample 3A represents the invention, theother samples are comparative.

    ______________________________________                                        Sample                                                                              Anhydride  Epoxy Resin.sup.a                                                                         Initiator.sup.b                                                                      Accelerator.sup.c                         ______________________________________                                        3-A   MACAN (5.5)                                                                              5.0         0.22   0.11                                      3-B   Itaconic (10.0)                                                                          13.0        0.65   0.235                                     3-C   Itaconic (10.0)                                                                          14.0        0.65   none                                      3-D   Maleic (10.0)                                                                            14.0        0.50   0.245                                     3-E   Styrene (9.0)/                                                                           1.76        0.21   0.017                                           Maleic (1.0)                                                            3-F   Styrene (6.0)/                                                                           7.0         0.20   0.07                                            Maleic (4.0)                                                            ______________________________________                                         .sup.a ERL4221                                                                .sup.b Vazo 52                                                                .sup.c benzyldimethylamine (BDMA)                                        

The mixture of Example 3-B began to gel upon admixture of the BDMA. Itwas therefore unsuitable for B staging and was not studied further. Theother samples were admixed as in Example 1.

Castings of the mixtures of Samples 3A, C, D, E, and F were prepared asin Example 1, except that the mold was heated overnight at 50° C. toassure completion of the B staging vinyl polymerization. Sample 3-Eseparated into two phases during this "B"-staging polymerization, makingit unsuitable for further cure into a resin useful for encapsulationpurposes.

The remaining "B"-stage samples were visually examined for the presenceof undesirable voids and for flow behavior by heating the samples in apress at 250° C. to determine if the material flowed. These tests are ameasure of the utility of the B stage for storage and furtherfabrication/curing.

The only sample which produced a useful B stage encapsulating productwithout voids and having the ability to flow when subjected to hightemperatures, as would be encountered in commercial encapsulationapplications, was sample 3-A of the invention.

The results are presented below in Table I.

                  TABLE I                                                         ______________________________________                                        Sample  Appearance      Voids?     Flow?                                      ______________________________________                                        3-A     Clear           no         yes                                        3-C     Clear           yes        no                                         3-D     Clear           yes        no                                         3-F     Clear           yes        no (a)                                     ______________________________________                                         (a) On heating to 175° C. overnight to complete cure, casting          became very brittle and darkened.                                        

EXAMPLE 4(Comparative) Torsional Braid Analysis

Measurement of properties of prior Samples 3A, C-F coated onto glassbraids were performed on an automated Torsional Braid Apparatus (TBA)sold by Plastics Analysis Instruments, Inc., Princeton, N.J. Thisapparatus, developed by J. K. Gilham, has been described in manypublications; an excellent review of the technique and experimentaltechnique used is found in a Chapter 5 of "Developments in PolymerCharacterisation 3", ed. J. V. Dawkins, Applied Science Publishers,Ltd., Barking, Essex, England (1982).

Other portions of Samples 3A, and C-F, other than those used to preparecastings in example 3, were poured into the molds of Example 1 and aglass braid was coated with each sample. The coated glass braids werethen inserted into the Torsional Braid Apparatus and each coated glassbraid sample was heated from room temperature at a rate of 2° C./minuteto 250° C. Rigidity and log decrement was measured while cooling each ofthe samples from 250° C. to room temperature at 2° C./minute decrements.The curing behavior and rigidity as a function of cure and temperature,and final glass transition temperature was reported. Curing results fromthe TBA are tabulated below (Table II). A Tg of above 150° C. is aminimum target for many of the uses contemplated for this invention.

                  TABLE II                                                        ______________________________________                                              Second-Stage                                                                  Curing Seen Tg, °C.                                                                             Softening during                               Sample                                                                              in TBA Curve?                                                                             of Final Product                                                                           temp. increments.sup.(a)                       ______________________________________                                        3-A   Yes         175          Yes                                            3-C   Yes         170          No                                             3-D   Yes.sup.(b)  75          Yes                                            3-E   Little/none ca. 105      Yes                                            3-F   Yes         ca. 145      Yes                                            ______________________________________                                         .sup.(a) Defined as a lower modulus (calculated from rigidity) with           absence of thermoset properties in the temperature range ca. 100°      C.-150° C. prior to final curing.                                      .sup.(b) Little increase in rigidity before reaching 100° C.           Indicates lack of firststage cure.                                       

The TBA indicates that while sample 3A of the invention softened andflowed (confirming the casting behavior of example 3A) when heated from100° C. to 150° C., it resulted in a solid thermoset having a Tg ofabout 175° C. Comparative examples 3D & 3E resulted in thermosets havinginsufficiently low Tgs (75° C. to 105° C.). Comparative example 3B whileexhibiting a high service temperature did not soften upon heatingindicating no adequate B stage formation. This result was consistentwith casting behavior from example 3. Comparative example 3F exhibited alower service temperature of about 145° C. and softened duringtemperature increments, but did not form a useful B stage material asexmplified in the casting experiment 3F.

EXAMPLE 5 Printed Circuit Board Mfg. UV Cure

Methacrylic anhydride (12 g), epoxycyclohexyl epoxycyclohexanoate (14.2g), 1-hydroxycyclohexyl phenyl ketone photoinitiator (0.12 grams,commercially known as Darocur®) and benzyltriethylammonium chlorideaccelerator (BTEAC) (0.12 grams) were mixed. The molar ratio of MACAN toepoxy was 0.8 to 1. The resulting solution was degassed and used toimpregnate a glass fabric. The impregnated glass fabric was placed in anitrogen atmosphere under a "black light" as a source of ultravioletlight (1.47 mW/cm2). The solution gelled within 20 minutes at roomtemperature to form a prepreg which was then cut into sections, stacked,and heated at 250° C. in a laminating press to form a laminate with a Tgof about 225° C.

EXAMPLE 6 UV Photoinitiator Variance:

The composition of Example 5 was reformulated with changes in the thelevel and type of photoinitiator with the results shown in Table III.

                                      TABLE III                                   __________________________________________________________________________    Initiator            Level                                                                              TIME TO GEL                                         Trade Name/Chemical Name                                                                           (Wt. %)                                                                            (Minutes)                                                                              Tg °C.                              __________________________________________________________________________    Darocur/1-hydroxycyclohexylphenyl ketone                                                           1    <20      225                                        Darocur/1-hydroxycyclohexylphenyl ketone                                                           5    <10      225                                        Irgacure ®/dimethoxyphenyl acetophenone                                                        1    <20      225                                        Irgacure ®/dimethoxyphenyl acetophenone                                                        5    <10      225                                        2,2-diethoxyacetophenone (DEAP)                                                                    1    <20      225                                        2,2-diethoxyacetophenone (DEAP)                                                                    5    <10      225                                        __________________________________________________________________________

EXAMPLE 7 UV Exposure Variation

The conditions of Experiment 5 were repeated again, except that theintensity of the ultraviolet light was varied from 0.2 mW/cm2 to 22mW/cm2 with no discernible effect on either the time to gelation or theTg.

EXAMPLE 8 Molar Ratio Epoxide/Anhdride Variance

The molar ratios of epoxy/anhydride of Example 5 was varied to about 0.6and about 1.0. The Tg of the resulting laminate was essentiallyunchanged over this compositional range.

EXAMPLE 9 Die Attach Adhesive

A die attach formulation viscous paste was prepared containing MACAN(25.5 g), ERL 4221 (31.7 g), Darocur (1.3 g), and BTEAC (1.3 g) mixedwith zirconium silicate filler (TAM-51418) (145.5 g). The resultingviscous paste was degassed and gelled under UV light to form an adhesivesolid. A small piece of the resulting adhesive solid was then placed ona heated (175° C.) ceramic substrate and a small silicon chip wasplaced, with gentle pressure, on top of the adhesive. After curing at175° C. for at least 2 hours the resulting bond had a pull strength ofabout 8 kilograms using a Semiconductor Equipment Corporation, model6000 Die Shear Tester.

We claim:
 1. A B-stage thermosettable composition comprising apolyepoxide and a cyclopolymerized linear anhydride monomer, where saidlinear anhydride monomer cyclopolymerizes with itself in the presence ofsaid polyepoxide without significant crosslinking with said polyepoxideto form the the thermoplastic B-stage composition which is stable uponstorage at room temperature and which produces a high servicetemperature thermoset by the reaction of said cyclopolymerized anhydridewith said polyepoxide upon curing, and where the molar ratio of saidlinear anhydride monomer to polyepoxide ranges from about 0.4/1 to 1/1.2. The composition of claim 1 wherein said linear anhydride monomer is(meth)acrylic anhydride.
 3. The composition of claim 1 furthercomprising an accelerator.
 4. The composition of claim 3 where theaccelerator is an aralkyltrialkyl quaternary ammonium halide.
 5. Thecomposition of claim 1 further comprising from about 0.1 to about 5.0weight percent of a free radical initiator.
 6. The composition of claim1 where the polyepoxide is selected from the group consisting ofepoxycyclohexyl epoxycyclohexanoate andbis(epoxyalkyl)polyhalodiphenylalkane.
 7. The composition of claim 1where the molar ratio of noncyclic anhydride to polyepoxide is fromabout 0.6/1 to 1/1.
 8. The composition of claim 1 further comprisingless than about 80 weight percent reinforcing agents, fillers, ordiluents.
 9. The composition of claim 6 wherein the reinforcing agent isa glass or aromatic polyamide.